The invention relates to an improved passive matrix super-twist nematic (STN) liquid crystal display (LCD), and more particularly, to a compensated normally white (NW) STN LCD.
Active matrix LCDs (AMLCDs) exhibit high contrast and stable chromaticity over a wide range of viewing angles, but frequently cost more than the market for mobile displays can bear. Mobile LCD markets such as the commercial aircraft and the automobile markets necessitate lower cost displays. Passively addressed (i.e., using multiplexed addressing techniques) STN LCDs cost less than AMLCDs, and therefore are an attractive alternative in certain LCD markets. STN LCDs are well-known in the art. See for example, Scheffer and Nehrin, Liquid Crystals Applications and Uses, B. Bahadhur, ed., 1990, p 231.
Normally black (NB) STN LCDs (commonly referred to as "film-compensated STN" or "FSTN" displays) and uncompensated NW STN LCDs (commonly referred to as optical mode interference or OMI displays) are examples of comparatively low-cost displays that can be driven by passive addressing techniques. Compared to NW STN LCDs, FSTN LCDs have more limited operational temperature ranges and exhibit large chromaticity shifts over the field-of-view (FOV). While NW STN LCDs are known to possess a wider operational temperature range than FSTN LCDs, they suffer from low display brightness and large chromaticity shifts over the range of viewing angles and of operating temperatures. These disadvantages of prior art NW STN LCDs limit their use in applications such as the commercial aircraft and automobile markets, to name just a few. Therefore, there is a need for a NW STN LCD which overcomes these limitations of prior art NW STN LCDs.